To Inspect Live Utility Lines, Send In the Robots

WHEN workers inspect utility lines, they must travel in special trolleys along transmission lines pulsing with up to 735,000 volts of electricity for a close-up view, or peer at the lines through binoculars from helicopters, trucks, all-terrain vehicles and snowmobiles, a method that misses small but potentially serious faults.

Using a robot for such harrowing work may seem like an obvious idea.

Indeed, Hydro Québec, a major exporter of electricity to the northeastern United States, now has five robots to inspect and even do small repairs along its 18,000 miles of distribution lines, the largest such network in North America. But creating the LineScout, which resembles an Erector Set project gone wild, proved to be anything but easy.

The device had to withstand high voltages that can fry electronics and create havoc with radio control systems, as well as the extreme weather in the province’s far north, home to most of its electrical generation dams. Most critically, the LineScout needed a way to maneuver around transmission towers and a variety of devices attached to the electrical lines.

“It took a year of thinking before we built any prototypes,” said Serge Montambault, a mechanical engineer with Hydro Québec’s research institute here, who leads the LineScout project. “Seven years later, I honestly think we’ve hit the bull’s-eye.”

Hydro Québec started the project largely to find a way to perform close-up inspections without cutting power on any of its lines. While line workers can use special insulated trolleys to move along live lines — which carry their electrical power through strands of aluminum wire on their exterior — cutting off the electricity before sending up inspectors remains the best practice, for obvious reasons.

For Hydro Québec, cutting power means lost export revenue. And for many utilities in the United States, it can lead to power shortages for customers.

“It’s become harder to build major lines,” said Thomas R. Kuhn, president of the Edison Electric Institute, an electrical utilities association based in Washington that awarded a prize to the LineScout last year. “But with everything becoming electronic, demand is increasing.”

Of all the problems that needed solving, Mr. Montambault said, finding a way of getting the robot around obstacles was among the most important. Long-distance electrical lines present robots with an aerial obstacle course. The most obvious hurdles are the large porcelain insulators that suspend the cables at every tower and prevent the electrocution of anyone on the ground. But other devices bolted to the lines keep cables separated (high-voltage, long-distance lines often use bundles of four wires in close proximity), minimize wind damage and, in the case of orange balls, ward off helicopters and other low-flying aircraft.

The researchers’ answer is mechanical ballet of sorts. Pincers, similar to those on insects, grip the power line to keep the robot from plunging to the ground while it lifts its two wheels off the power line and then swings them around to the other side of the obstruction. The action is more complex than it sounds and is controlled by an operator on the ground using a combination of handgrips, a video display and a touch-screen laptop computer.

Photo

SKYWALKER A worker for Hydro Québec places a LineScout robot on a transmission cable for testing.Credit
Courtesy of Hydro Qu�bec

The research group decided that, because the robot would be largely made from conductive metals, it was better for it to become electrically charged than to insulate it from the electricity running through the lines. A charged robot eliminated the possibility of large and potentially damaging electrical arcs between the machine and the lines. Rubber, although it is an electrical insulator, is also the only material able to provide sufficient grip for the robot’s wheels, its contact with the line. To solve that problem, researchers at Goodyear created a conductive rubber compound that includes silver.

The LineScout’s four video cameras, and a fifth infrared camera that detects hot spots along the line, beam images down to a portable control station on the ground. They are viewed live and recorded for closer examination later. The LineScout can also wrap and temporarily clamp frayed strands of conductor wires, measure the electrical resistance of splices along the line and tighten bolts on the various devices clamped to the wires.

The LineScout does, however, have one significant limitation. To limit the toppling domino effect that follows the collapse of a transmission tower after, say, an ice storm, the lines are anchored to, rather than suspended from, strengthened towers every 10 to 15 miles. Those anchor towers are the one obstacle that the LineScout cannot bypass.

And while its inspections are detailed, the LineScout takes its time. The longest stretch a LineScout has inspected in a day is just over five miles. For more sweeping, less detailed infrared inspections, Mr. Montambault has been looking at drone aircraft, although civil aviation rules in North America and Europe remain a hurdle.

BC Hydro, Hydro Québec’s counterpart in the province of British Columbia, also uses the LineScout, particularly to inspect lines that span exceptionally wide water crossings, and has become an investor in the device.

Because the LineScout moves at such a stately pace, Kip Morison, the chief technology officer at BC Hydro, said his firm would probably use it only to inspect lines that were difficult to reach, like those that cross long stretches of water, or that were especially prone to deterioration. “It’s not likely that it will replace helicopter inspections for our 18,000-kilometer network,” he said, referring to the utility’s nearly 11,200 miles of lines.

Mr. Morison said, however, that the LineScout uncovered potentially serious early fraying problems on a line that other inspection methods would have missed.

There are enough researchers developing electrical line robots that a conference on the subject was held last year in Montreal. But the LineScout, Mr. Montambault said, remained the only commercially available model that could operate on live lines.

At Hydro Quebéc’s lab, Mr. Montambault is continuing to develop new versions of the robot, which will include greater automation, more sensors and the ability to perform permanent repairs. Increasingly, he said, researchers were also dealing with other utilities interested in collaborating on the project.

“It’s very rewarding to see this on our network, but also to have other people coming to us and saying ‘We want to play with you guys.’ ”

A version of this article appears in print on October 26, 2011, on page F3 of the New York edition with the headline: To Inspect Live Utility Lines, Send in the Robots. Order Reprints|Today's Paper|Subscribe